1. Field of the Invention
This invention relates to comminuting or shredding apparatuses, and particularly to shredders having a plurality of rotating rolls provided with teeth. Most particularly, the shredder is of a type for shredding waste wood such as pallets, crating, stumps and other construction material, for example cardboard and other organic material.
2. Description of the Prior Art
Traditionally, a rotating roll comminuting apparatus has one or more rolls provided with teeth or other protrusions, which cooperate with non-rotating anvil structures to break up material. Comminuting apparatuses of this type are disclosed in U.S. Pat. No. 3,703,970 (Benson), U.S. Pat. No. 5,320,293 (Laly et al.) and U.S. Pat. No. 5,094,392 (Szombathy), for example.
The traditional comminuting apparatuses all share a number of apparent disadvantages and drawbacks. They are relatively complicated in their roll teeth/anvil structure, which makes their manufacture expensive. When the roll teeth/anvil structure gets worn, it is complicated, and therefor expensive, to replace or repair this structure. The teeth have to be cut off and new teeth welded in place, or a new roll have to be installed and the old roll sent for repair.
It is an object of the invention to mitigate and/or obviate the above mentioned disadvantages and drawbacks to provide a shredding apparatus, which is easy and cheap to manufacture and assemble and which provides the required shredding capacity.
A further object of the invention is to provide a shredding apparatus, which spreads the material to be shredded over a large area of the plurality of rotating rolls, in order to enhance the output of the shredder and at the same time avoiding material bridging (material to be shredded is stuck above the rolls because it is squeezed by other pieces of material to be shredded, held by the surrounding walls etc.).
Yet a further object of the invention is to provide a shredding apparatus, which provides an axial flow of the material to be shredded along the longitudinal direction of the rolls, for further eliminate material gliding above the rolls.
Still a further object of the invention is to provide a shredding apparatus, which provides reversible rolls having equal shredding capabilities in either direction of rotation, to effect reflow and agitation of the material to be shredded.
Another object of the invention is to provide a shredding apparatus, which controls the depth of the cut of the shredding rolls into the material to be shredded.
A further object of the invention is to provide a shredding apparatus, in which the smaller size material, which is not required to be sized, freely falls through the shredding roll construction, to reduce wear and tear on the rolls.
In the invention, a shredding apparatus comprises a plurality of rotatable rolls, each one of the rolls being rotatable around an axis of rotation in a first direction of rotation or a second direction of rotation. Each roll further has a plurality of angled replaceable teeth, which are arranged in at least one first set of teeth arranged in a first helical line across an outer surface of each roll, circumferentially spaced apart a first angle and facing the first direction of rotation. Further, at least one second set of teeth is arranged in a second helical line across the outer face of each roll, circumferentially spaced apart the first angle and facing the second direction of rotation. The first helical line and the second helical line of teeth are arranged to axially (in the longitudinal direction of the rolls) move material to be shredded when the rolls are rotated. Further, the shredding apparatus has a frame structure with roll holding means, for journalling the plurality of rolls in a spaced apart relationship to form a bed of rolls. The frame structure is surrounded by an enclosure provided with a charging opening for material to be shredded and a discharging opening for shredded material. A reversible drive means supplies rotation force to rotate the plurality of rolls, and a plurality of gear means, arranged one for each roll, transfers the rotation force from one roll to an adjacent roll so that adjacent rolls rotate in opposite directions of rotation.
The plurality of rolls preferably comprises at least 4 rolls, preferably 4, 6, 8, 10, 11 or 12 rolls.
The first angle is preferably 15, 30, 45, 60 or 90 degrees.
Each roll is advantageously arranged on the frame roll holding means so that each of the at least one first and at least one second helical line of teeth is offset a second angle with respect to the at least one first and at least one second helical line of teeth of adjacent rolls. The second angle is preferably 6, 8, 10 or 12 degrees.
Each roll arranged in a middle portion of the bed of rolls is preferably held in a lower position compared to the rolls arranged towards either of two outer sides of the bed of rolls, forming sloping sides of the bed of rolls down towards the middle of the bed of rolls in the longitudinal direction of the bed of rolls, to force material to be shredded to be moved from the outer sides to the middle portion of the bed of rolls. Thus, the bed of rolls is shaped as a curve, having the outer rolls at a higher elevation than the middle rolls.
The teeth of the at least one first and the at least one second set of teeth of each of the rolls are preferably arranged so that only one tooth is engaging the material to be shredded at one time during the rotation of the roll. Alternatively, the teeth of the at least one first and the at least one second set of teeth of each of the rolls are arranged so that at least two teeth are engaging the material to be shredded at one time during the rotation of said roll.
The rolls further preferably have sizing discs arranged around a circumference of each roll, the sizing discs being positioned along the outer surface of each roll, where each sizing disc of one roll is placed so that sizing discs of an adjacent roll do not occupy the same space as the sizing discs of the one roll.
In one embodiment of the invention, the reversible drive means comprises at least one internal combustion engine. Alternatively, the reversible drive means comprises at least one electric motor, at least one hydraulic motor or at least one pneumatic motor. In a further embodiment of the invention, the reversible drive means comprises a first hydraulic cylinder and a second hydraulic cylinder, the first cylinder being anchored at one end and attached to a first gear means of a first roll at a first off-centre mounting means on the first gear means, the second cylinder being anchored at one end and attached to a second gear means of a second roll at a second off-centre mounting means on the second gear means, so that when the first cylinder is extended or retracted, the first gear means is made to rotate around the axis of rotation for the first roll, and when the second cylinder is extended or retracted, the second gear means is made to rotate around the axis of rotation for the second roll, causing the plurality of rolls to rotate driven by the plurality of gear means for each roll. The first off-centre mounting means and the second off-centre mounting means are arranged at different angular locations on the first and second gear means, respectively, to prevent stalling of rotation force transfer from the first and second cylinders.
The reversible drive means further advantageously comprises a pressure sensing means connected to automatically reverse the roll rotation directions when the pressure sensing means senses that material to be shredded is stuck in the plurality of rolls.
The reversible drive means further preferably comprises a timer arrangement to periodically reverse the roll rotation direction.
The shredding apparatus further comprises a plurality of vertically extendible/contractible and horizontally spaceable main legs, to provide support for the shredding apparatus during shredding, and a plurality of extendible and contractible lifting legs, to lift the shredding apparatus off ground, so that the main legs can be spaced apart and extended or contracted and spaced together for providing self-loading and self-erecting capabilities to the shredding apparatus.
Preferably, the main legs comprise a first leg assembly and a second leg assembly, arranged on opposite sides of the frame. The first leg assembly comprises a first main housing attached to the frame via first frame extensions, a first main leg extending from the first main housing, protruding substantially downwards, at a first end of the first main housing and a second main leg, protruding substantially downwards, from a second end of the first main housing. The first main leg is held by a first holding means, slidingly arranged in the first main housing at the first end, between a retracted position and an extended position. The second main leg is held by a second holding means, slidingly arranged in the first main housing at the second end, between a retracted position and an extended position. The second leg assembly comprises a second main housing attached to the frame via second frame extensions. A third main leg extends from the second main housing, protruding substantially downwards, at a third end of the second main housing and a fourth main leg, protrudes substantially downwards, from a fourth end of the second main housing. The third main leg is held by a third holding means, slidingly arranged in the second main housing at the third end, between a retracted position and an extended position. The fourth main leg is held by a fourth holding means, slidingly arranged in the second main housing at the fourth end, between a retracted position and an extended position.
The sliding motion of the first holding means and the second holding means is preferably provided by at least one first fluid cylinder arranged inside the first main housing, and the sliding motion of the third holding means and the fourth holding means is preferably provided by at least one second fluid cylinder arranged inside the first main housing.
A first lifting leg and a second lifting leg are preferably arranged at the first frame extension, the first lifting leg and the second lifting leg being extendably arranged in a downward direction, between a fully retracted position and a fully extended position. The first lifting leg and the second lifting leg are extendable further downwards than the first main leg and the second main leg. A third lifting leg and a fourth lifting leg are preferably arranged at the second frame extension, the third lifting leg and the fourth lifting leg being extendably arranged in a downward direction, between a fully retracted position and a fully extended position. The third lifting leg and the fourth lifting leg are extendable further downwards than the third main leg and the fourth main leg.
The rolls are preferably arranged with their longitudinal direction running from the first leg assembly to the second leg assembly. Alternatively, the rolls are arranged with their longitudinal direction perpendicular to a line connecting the first leg assembly and the second leg assembly.
The enclosure advantageously comprises four substantially horizontal walls, the rolls forming the entire bottom part of the enclosure, so that material to be shredded only flows through the rolls.
Further features of the invention will be described or will become apparent in the course of the following detailed description.